Fast charge long-lifetime secondary battery, battery module, battery pack, and power consumption device

ABSTRACT

The present disclosure provides a fast charge long lifetime secondary battery, a battery module, a battery pack, and a power consumption device. In some embodiments, a secondary battery, comprising an electrode assembly and an electrolytic solution, the electrode assembly comprises a positive electrode plate, a negative electrode plate, and a separator, the positive electrode plate comprises a positive electrode tab, and the negative electrode plate comprises a negative electrode tab are provided. In those embodiments, the positive electrode tab has the following temperature rise coefficient:α=C1⁢0⁢S⁢1where S1 is a total cross-sectional area of the positive electrode tab, in unit of mm2; C is capacity of the electrode assembly, in unit of A·h; the electrolytic solution contains a heat stable salt and an additive that inhibits decomposition of the lithium salt.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International ApplicationPCT/CN2021/119110, filed Sep. 17, 2021 and entitled “FAST CHARGELONG-LIFETIME SECONDARY BATTERY, BATTERY MODULE, BATTERY PACK, AND POWERCONSUMPTION DEVICE”, the entire content of which is incorporated hereinby reference.

TECHNICAL FIELD

The present disclosure relates to the technical field of batteries, andin particular, to a fast charge long-lifetime secondary battery, abattery module, a battery pack, and a power consumption device.

BACKGROUND ART

The lithium-ion batteries are widely applied in various fields such asnew-energy vehicles and energy storage power stations due to theadvantages such as high energy density, long lifetime, and energy savingand environmental friendliness. With the accelerated pace of life andthe development of electronic products, consumers more urgently need toshorten the charge time and increase the discharge power of thelithium-ion batteries, i.e. to increase the C-rate of the batteries.However, increasing the C-rate of the batteries will cause significantincrease in temperature rise coefficient at the tab inside the batterycore, further lead to relatively high temperature rise at the tab, andcause accelerated decomposition of the electrolytic solution around thetab into high active substances such as HF and PF₅, not only resultingin a decreased content of lithium salts, but also further damaging SEIand speeding up the consumption of the electrolytic solution. This willlead to an insufficient electrolytic solution content, insufficientdynamics of the battery core, and corresponding rapid increase in SEIimpedance after the battery core has been cycled for a period of time,and finally result in deterioration of power and performances of thebattery core after the cycling, which is manifested by rapid increase ininternal resistance of the battery core. Besides, with the consumers'demand for high-energy-density battery cores, the current at the tab ofthe battery core is larger when charging and discharging at the samerate, further resulting in a larger temperature rise coefficient of thetab.

SUMMARY

The present disclosure is carried out in view of the above subjects, andone of the objectives is to provide a fast charge long-lifetimesecondary battery, which still can maintain relatively high power andperformances in middle and later stages of the cycle.

In order to achieve the above objectives, the present disclosureprovides a secondary battery, a battery module containing the secondarybattery, a battery pack containing the battery module, and a powerconsumption device containing the secondary battery, the battery moduleor the battery pack.

In a first aspect, the present disclosure provides a secondary battery,including an electrode assembly and an electrolytic solution, theelectrode assembly including a positive electrode plate, a negativeelectrode plate, and a separator, the positive electrode plate includinga positive electrode tab, and the negative electrode plate including anegative electrode tab, wherein the positive electrode tab has thefollowing temperature rise coefficient α A·h/mm:

$\alpha = \frac{C}{10\sqrt{S1}}$

-   -   where S1 is a total cross-sectional area of the positive        electrode tab, in unit of mm²; C is capacity of the electrode        assembly, in unit of A·h (ampere-hour);    -   the electrolytic solution contains a heat stable salt and an        additive that inhibits decomposition of the lithium salt,    -   in the above, the heat stable salt has the following molecular        formula:        (M^(y+))_(x/y)R₁(SO₂N)_(x)SO₂R₂,    -   where M^(y+) is one or more selected from the group consisting        of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Ba²⁺, Al³⁺, Fe²⁺, Fe³⁺,        Ni²⁺, and Ni³⁺, optionally, M^(y+) is one or more selected from        the group consisting of Li⁺, K⁺, Cs+, and Ba²⁺, and y is valence        of the M;    -   the R₁ and R₂ are each independently selected from the group        consisting of fluorine atom, fluoroalkyl having 1˜20 carbon        atoms, fluoroalkoxy having 1˜20 carbon atoms, and alkyl having        1˜20 carbon atoms,    -   x is an integer selected from the group consisting of 1, 2, and        3,    -   by mass percentage, a content of the heat stable salt in the        electrolytic solution is w %;    -   the additive that inhibits decomposition of lithium salt is one        or more of RSO₃F, where R is one or more selected from the group        consisting of Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺,    -   by mass percentage, a content of the additive that inhibits the        decomposition of lithium salt in the electrolytic solution is        m₁%, and    -   the w, m₁, and α satisfy 0.5<m₁w/α<20, and optionally satisfy        1<m₁w/α<14.

In some embodiments, α may be 2˜9.5. With the α being within the abovenumerical ranges, the following cases can be avoided: if α is too high,the positive electrode tab possibly can hardly bear a current valueunder high magnification, and the tab is easy to fuse; and if α is toolow, the tab may occupy a large volume of the battery core, and thevolume energy density of the battery core is too low.

In some embodiments, the mass fraction m₁% of the additive RSO₃F thatinhibits the decomposition of lithium salt may be 0.1%˜10%, optionally0.2%˜5%. With the m₁ being within the above ranges, the following casescan be avoided: if m₁ is too low, it may be insufficient to inhibit thedecomposition of lithium salt, resulting in poor heat stability of theelectrolytic solution, and if m₁ is too high, the conductivity of theelectrolytic solution may be significantly deteriorated, the dynamics ofthe electrolytic solution is insufficient, the polarization duringhigh-rate charge and discharge is large, the discharge power isdeteriorated, lithium precipitation of the battery core is furthercaused in severe cases, and the cycle performances are deteriorated.

In some embodiments, the concentration w % of the stable lithium saltmay be 8%˜30%, optionally 10%˜23%. With the w % being within the aboveranges, the following cases can be avoided: if the concentration of thestable lithium salt is too low, it may not be sufficient to improve theheat stability of the electrolytic solution, and if the concentration istoo high, the concentration of the electrolytic solution may be toohigh, further the dynamics of the electrolytic solution is deteriorated,and the charge and discharge power of the battery core is deteriorated.

In some embodiments, the heat stable salt has a temperaturecorresponding to 5% weight loss rate higher than 200° C.

In some embodiments, in the molecular formula of the heat stable salt,x=1 and y=1, or x=1 and y=2, or x=2 and y=1.

In some embodiments, in the molecular formula of the heat stable salt,R₁ and R₂ are each independently selected from fluorine atom andtrifluoromethyl; and optionally, R₁ and R₂ are both fluorine atoms orboth trifluoromethyl.

In some embodiments, the heat stable salt is one or more selected fromthe group consisting of: lithium bisfluorosulfonyl imide, potassiumbisfluorosulfonyl imide, cesium bisfluorosulfonyl imide, bariumbisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide,Li₂F(SO₂N)₂SO₂F, and LiCF₃SO₂NSO₂F.

In some embodiments, the additive that inhibits the decomposition oflithium salt is one or more of LiSO₃F, NaSO₃F, or KSO₃F.

In some embodiments, the electrolytic solution further may contain afluorinated solvent, and the fluorinated solvent is one or more selectedfrom the group consisting of fluorinated carbonate, fluorobenzene, andfluoroether. The fluorinated solvent can be used for reducing theelectron cloud density of the stable lithium salt, improving theelectrochemical stability of the stable lithium salt after solvation,and further reducing the decomposition and consumption of theelectrolytic solution. The content of the fluorinated solvent in theelectrolytic solution is m₂%, and optionally, a ratio m₂/α of m₂ to α is1˜8.

In some embodiments, the fluorinated carbonate is

and/or, the fluorobenzene is

and/or, the fluoroether is R_(1′)—O—R_(2′), where R₃, R₄, R₅, R₆,R_(1′), and R_(2′) are each independently —C_(x′)F_(y′)H_(z′), 1≤x′≤6,y′>0, z′>0, and 0≤y′≤2x′, 0≤z′≤2x′, and R₇, R₈, R₉, R₁₀, R₁₁, and R₁₂are each independently one of F or H.

In some embodiments, R_(1′) and R_(2′) are each independently selectedfrom the group consisting of —C₂F₄H, —CF₃, —C₃F₆H, —C₂F₃H₂, and —C₃F₄H₃;optionally, R_(1′) and R_(2′) are each independently selected from thegroup consisting of —CF₂—CF₂H, —CF₃, —CF₂—CFH—CF₃, —CH₂—CF₃, and—CH₂—CF₂—CHF₂; and optionally, the fluoroether is selected from thefollowing structures:

In some embodiments, R₅ and R₆ are each independently selected from thegroup consisting of —C₂F₃H, —CFH, and —CH₂; optionally, R₅ and R₆ areeach independently selected from the group consisting of —CH—CF₃, —CHF,and —CH₂; and optionally, the fluorinated carbonate is selected from thegroup consisting of:

In some embodiments, R₅ and R₆ are each independently selected from thegroup consisting of —CH₃, —C₂F₃H₂, —CFH₂, and —C₂FH₄; optionally, R₅ andR₆ are each independently selected from the group consisting of —CH₃,—CH₂—CF₃, —CH₂—F, and —CH₂—CH₂—F; and optionally, the fluorinatedcarbonate is selected from the group consisting of:

In some embodiments, the electrolytic solution further may contain anadditive prone to lose electrons to be oxidized, and the additive proneto lose electrons is one or more selected from the group consisting ofphosphite, borate, and phosphate. The additive prone to lose electronsto be oxidized can be oxidized into a film earlier than the stablelithium salt, and further the decomposition of stable lithium salt isreduced. A content of the additive prone to lose electrons in theelectrolytic solution is m₃%, and optionally, a ratio m₃/α of m₃ to α is0.1˜0.9.

In some embodiments, the phosphite is

and/or, the phosphate is

and/or, the borate is

where R₁₃, R₁₄, R₁₅, R₁₆, R₁₇, R₁₈, R₁₉, R₂₀, and R₂₁ are eachindependently selected from the group consisting of: alkyl, fluoroalkyl,silyl, alkenyl, and phenyl.

In some embodiments, R₁₃, R₁₄, and R₁₅ are each independently selectedfrom the group consisting of C₁₋₆ alkyl (e.g., methyl, ethyl) and C₁₋₆fluoroalkyl (e.g., fluoromethyl, fluoroethyl, e.g., —CH₂—CF₃); andoptionally, the phosphite is selected from

In some embodiments, R₁₆, R₁₇, and R₁₈ are each independently selectedfrom C₁₋₆ fluoroalkyl (e.g., fluoromethyl, fluoroethyl, e.g., —CH₂—CF₃)and C₁₋₆ alkenyl (e.g., allyl); and optionally, the phosphate isselected from:

In some embodiments, R₁₉, R₂₀, and R₂₁ are each independently selectedfrom the group consisting of C₁₋₆ alkyl (e.g., methyl, ethyl) and C₁₋₆fluoroalkyl (e.g., fluoromethyl, fluoroethyl, e.g., —CH₂—CF₃); andoptionally, the borate is selected from

In a second aspect, the present disclosure provides a battery module,including the secondary battery in the first aspect of the presentdisclosure.

In a third aspect, the present disclosure provides a battery pack,including the battery module in the second aspect of the presentdisclosure.

In a fourth aspect, the present disclosure provides a power consumptiondevice, including the secondary battery in the first aspect of thepresent disclosure, the battery module in the second aspect of thepresent disclosure, or the battery pack in the third aspect of thepresent disclosure.

The secondary battery provided in the present disclosure can inhibit thedecomposition of the electrolytic solution at the tab, significantlyimprove the heat stability of the electrolytic solution, reduce thedecomposition of the electrolytic solution at high temperatures, prolongthe lifetime of the battery core, and solve the problem that thelifetime of the battery core is shortened caused by heat release of thetab during fast charge of the battery core.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a secondary battery in an embodiment ofthe present disclosure.

FIG. 2 is an exploded view of the secondary battery in an embodiment ofthe present disclosure shown in FIG. 1 .

FIG. 3 is a schematic view of a battery module in an embodiment of thepresent disclosure.

FIG. 4 is a schematic view of a battery pack in an embodiment of thepresent disclosure.

FIG. 5 is an exploded view of the battery pack in an embodiment of thepresent disclosure shown in FIG. 4 .

FIG. 6 is a schematic view of a power consumption device using thesecondary battery in an embodiment of the present disclosure as a powersupply.

REFERENCE SIGNS

1 battery pack; 2 upper box body; 3 lower box body; 4 battery module; 5secondary battery; 51 housing; 52 electrode assembly; 53 cover plate

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure are further described in detailbelow in combination with examples. The following detailed descriptionof the examples are used to exemplarily illustrate the principle of thepresent disclosure, but cannot be used to limit the scope of the presentdisclosure, that is, the present disclosure is not limited to theexamples described.

Hereinafter, the embodiments disclosing a secondary battery and amanufacturing method thereof, a battery module, a battery pack, and apower consumption device in the present disclosure are described indetail. However, unnecessary detailed descriptions may be omitted insome cases. For example, there are cases where detailed descriptions ofwell-known items and repeated descriptions of actually identicalstructures are omitted. This is for the purpose of avoiding thefollowing descriptions becoming unnecessarily lengthy and facilitatingthe understanding of those skilled in the art.

The “range” disclosed in the present disclosure is defined in the formof a lower limit and an upper limit, a given range is defined byselecting a lower limit and an upper limit, and the selected lower limitand upper limit define boundaries of a particular range. A range definedin this manner may include end values or not, and may be arbitrarilycombined, i.e., any lower limit may be combined with any upper limit toform a range. For example, if the ranges of 60˜120 and 80˜110 are listedfor a particular parameter, it is contemplated that the ranges of 60˜110and 80˜120 are also expected. Besides, if the minimum range valueslisted are 1 and 2, and the maximum range values listed are 3, 4, and 5,the following ranges can be all expected: 1˜3, 1˜4, 1˜5, 2˜3, 2˜4, and2˜5. In the present disclosure, unless otherwise stated, the numericalrange “a˜b” represents an abbreviation of combinations of any realnumbers between a and b, where a and b are both real numbers. Forexample, the numerical range “0˜5” indicates that all real numbers in“0˜5” have been all listed herein, and “0˜5” is just an abbreviation ofcombination of these numerical values. In addition, when a certainparameter is expressed as an integer greater than or equal to 2 (≥2), itis equivalent to disclosing that this parameter is, for example, aninteger such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

If without special illustration, all the embodiments and optionalembodiments of the present disclosure can be combined with each other toform a new technical solution.

If without special illustration, all the technical features and optionaltechnical features of the present disclosure can be combined with eachother to form a new technical solution.

If without special illustration, all steps of the present disclosure canbe carried out in sequence, and also can be carried out randomly,preferably in sequence. For example, if the method includes steps (a)and (b), it means that the method may include steps (a) and (b)performed in sequence, and also may include steps (b) and (a) performedin sequence. For example, the method referred to further may includestep (c), meaning that step (c) may be added to the method in any order,for example, the method may include steps (a), (b), and (c), also mayinclude steps (a), (c), and (b), and also may include steps (c), (a),and (b), etc.

If without special illustration, the terms “include (comprise)” and“contain” mentioned in the present disclosure is open-ended, and alsomay be close-ended. For example, the terms “include (comprise)” and“contain” may mean that other components that are not listed also may beincluded or contained, or only the listed components may be included orcontained.

If without special illustration, in the present disclosure, the term“or” is inclusive. For example, the phrase “A or B” means “A, B, or bothA and B”. More specifically, any of the following conditions satisfiesthe condition “A or B”: A is true (or present) and B is false (orabsent); A is false (or absent) and B is true (or present); or both Aand B are true (or present).

Second Battery

As introduced in the background, the secondary battery may be, forexample, a lithium-ion battery. In the fast charging process of theconventional lithium-ion battery, the tab releases heat seriously, theelectrolytic solution near the tab will be decomposed to generate acidichigh-activity substances such as HF and PF₅, and further the cycleservice lifetime of the battery core is obviously shortened. Besides,with the increase of volume energy density of the battery core, thetemperature rise coefficient of the tab of the battery is bigger, thedecomposition of the electrolytic solution at the tab is furtheraccelerated, and the lifetime of the battery core is shortened.

Generally, in the charging and discharging process, the decomposition ofthe electrolytic solution is directly proportional to the temperaturerise at the tab, and the greater the temperature rise at the tab is, themore serious the decomposition of the electrolytic solution is. Undercertain C-rate, the temperature rise at the tab of the battery core ismainly directly proportional to the resistivity and the battery corecapacity of the tab, and as a positive electrode tab is usually of analuminum-based material, and it has the resistivity far greater thannegative electrode tab (usually of a copper-based material), in thecharging and discharging process, the temperature rise of the positiveelectrode tab is usually relatively high.

In an embodiment of the present disclosure, a secondary battery isprovided, including an electrode assembly and an electrolytic solution,wherein the electrode assembly includes a positive electrode plate, anegative electrode plate, and a separator, the positive electrode plateincludes a positive electrode tab, and the negative electrode plateincludes a negative electrode tab; and in the above, the positiveelectrode tab has the following temperature rise coefficient α A·h/mm:

$\alpha = \frac{C}{10\sqrt{S1}}$where S1 is a total cross-sectional area of the positive electrode tab,in unit of mm²; C is capacity of the electrode assembly, in unit of A·h.S1 and C can be measured or tested by conventional methods in the art.

In some embodiments, α is 2˜9.5 (e.g. 2˜2.5, 2.5˜3, 3˜3.5, 3.5˜4, 4˜4.5,4.5˜5, 5˜5.5, 5.5˜6, 6˜6.5, 6.5˜7, 7˜7.5, 7.5˜8, 8˜8.5, 8.5˜9 or 9˜9.5).With the α being within the above numerical ranges, the following casescan be avoided: if α is too high, the positive electrode tab possiblycan hardly bear a current value under high magnification, and the tab iseasy to fuse; and if α is too low, the tab may occupy a large volume ofthe battery core, and the volume energy density of the battery core istoo low.

In the secondary battery in the present disclosure, the electrolyticsolution contains a heat stable salt and an additive that inhibitsdecomposition of the lithium salt. The heat stable salt cansignificantly improve the heat stability of the electrolytic solution,and reduce the decomposition of the electrolytic solution at hightemperatures. However, the heat stable salt is not resistant tooxidation, and is easily decomposed and consumed, resulting incontinuous decrease in the concentration of lithium salt in theelectrolytic solution and the total amount of the electrolytic solution.The inventors selected RSO₃F as an additive that inhibits thedecomposition of lithium salt, and could significantly inhibit thedecomposition of lithium salt with high heat stability.

In various embodiments, the heat stable salt in the present disclosurehas the following molecular formula:(M^(y+))_(x/y)R₁(SO₂N)_(x)SO₂R₂,

-   -   where M^(y+) is one or more selected from the group consisting        of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Ba²⁺, Al³⁺, Fe²⁺, Fe³⁺,        Ni²⁺, and Ni³⁺, optionally, M^(y+) is one or more selected from        the group consisting of Li⁺, K⁺, Cs⁺, and Ba²⁺, and y is valence        of the M;    -   the R₁ and R₂ are each independently selected from the group        consisting of fluorine atoms, fluoroalkyl having 1˜20 (e.g.,        1˜6) carbon atoms, fluoroalkoxy having 1˜20 (e.g., 1˜6) carbon        atoms, and alkyl having 1˜20 (e.g., 1˜6) carbon atoms, and    -   x is an integer selected from the group consisting of 1, 2, and        3.

By mass percentage, the content of the heat stable salt in theelectrolytic solution is w %. In some embodiments, w % may be 8%˜30%,optionally 10%˜23% (for example, 8%˜9%, 9%˜10%, 10%˜11%, 11%˜12%,12%˜13%, 13%˜14%, 14%˜15%, 15%˜16%, 16%˜17%, 17%˜18%, 18%˜19%, 19%˜20%,20%˜21%, 21%˜22%, 22%˜23%, 23%˜24%, 24%˜25%, 25%˜26%, 26%˜27%, 27%˜28%,28%˜29% or 29%˜30%). With the w % being within the above ranges, thefollowing cases can be avoided: if the concentration of the heat stablelithium salt is too low, it may not be sufficient to improve the heatstability of the electrolytic solution, and if the concentration of theheat stable lithium salt is too high, the concentration of theelectrolytic solution may be too high, further the dynamics of theelectrolytic solution is deteriorated, and the charge and dischargepower of the battery core is deteriorated.

The additive that inhibits the decomposition of lithium salt used in thepresent disclosure is one or more of RSO₃F, where R is one or moreselected from the group consisting of Li⁺, Na⁺, K⁺, Rb⁺, and Cs+.

By mass percentage, the content of the additive that inhibits thedecomposition of lithium salt in the electrolytic solution is m₁%. Insome embodiments, the mass fraction m₁% of the additive RSO₃F thatinhibits the decomposition of lithium salt may be 0.1%˜10%, optionally0.2%˜5% (for example, 0.1%˜0.2%, 0.2%˜0.4%, 0.4%˜0.6%, 0.6%˜0.8%,0.8%˜1%, 1%˜1.5%, 1.5%˜2%, 2%˜2.5%, 2.5%˜3%, 3%˜3.5%, 3.5%˜4%, 4%˜4.5%,4.5%˜5%, 5%˜6%, 6%˜7%, 7%˜8%, 8%˜9% or 9%˜10%). With the m₁ being withinthe above ranges, the following cases can be avoided: if m₁ is too low,it may be insufficient to inhibit the decomposition of lithium salt,resulting in poor heat stability of the electrolytic solution, and if m₁is too high, the conductivity of the electrolytic solution may besignificantly deteriorated, the dynamics of the electrolytic solution isinsufficient, the polarization during high-rate charge and discharge islarge, the discharge power is deteriorated, lithium precipitation of thebattery core is further caused in severe cases, and the cycleperformances are deteriorated.

Further, the inventors found through a large number of experiments thatw, m₁, and α satisfying 0.5<m₁w/α<20 can better solve the problem ofelectrolytic solution decomposition caused by heat release from the tabin the high-rate charge and discharge process of the battery core,reduce the total consumption of the electrolytic solution, and furtherpromote the power and performances of the battery core in the middlestage of cycle. In some embodiments, w, m₁, and α satisfy: 1<m₁w/α<14.In some embodiments, m₁w/α is 0.5˜0.6, 0.6˜0.7, 0.7˜0.8, 0.8˜0.9, 0.9˜1,1˜2, 2˜3, 3˜4, 4˜5, 5˜6, 6˜7, 7˜8, 8˜9, 9˜10, 10˜11, 11˜12, 12˜13,13˜14, 14˜15, 15˜16, 16˜17, 17˜18, 18˜19 or 19˜20.

In some embodiments, the heat stable salt has a temperature higher than200° C. corresponding to 5% weight loss rate. The relationship betweenthe weight and the temperature of the heat stable salt can be measuredby thermogravimetric analysis, to obtain the temperature correspondingto 5% weight loss.

In some embodiments, in the molecular formula of the heat stable salt,x=1 and y=1, or x=1 and y=2, or x=2 and y=1.

In some embodiments, in the molecular formula of the heat stable salt,R₁ and R₂ are each independently selected from fluorine atom andtrifluoromethyl. In some embodiments, R₁ and R₂ are both fluorine atomsor both trifluoromethyl.

In some embodiments, the heat stable salt is one or more selected fromthe group consisting of: lithium bisfluorosulfonyl imide (LiFSI),potassium bisfluorosulfonyl imide (KFSI), cesium bisfluorosulfonyl imide(CsFSI), barium bisfluorosulfonyl imide (Ba(FSI)₂), lithiumbistrifluoromethanesulfonyl imide (LiTFSI), Li₂F(SO₂N)₂SO₂F, andLiCF₃SO₂NSO₂F.

In some embodiments, the additive that inhibits the decomposition oflithium salt is one or more of LiSO₃F, NaSO₃F, or KSO₃F.

In the secondary battery of the present disclosure, the electrolyticsolution further may contain a fluorinated solvent for reducing theelectron cloud density of the stable lithium salt, further improving theelectrochemical stability of the stable lithium salt after solvation,and further reducing the decomposition and consumption of theelectrolytic solution. The fluorinated solvent can be one or moreselected from the group consisting of fluorinated carbonate,fluorobenzene, and fluoroether. The content of the fluorinated solventis m₂%, and a ratio m₂/α of m₂ to α is optionally 1˜8, for example,1˜1.5, 1.5˜2, 2˜2.5, 2.5˜3, 3˜3.5, 3.5˜4, 4˜4.5, 4.5˜5, 5˜6, 6˜7 or 7˜8.

In some embodiments, the fluorinated carbonate is

in some embodiments, the fluorobenzene is

and in some embodiments, the fluoroether is R_(1′)—O—R_(2′), where R₃,R₄, R₅, R₆, R_(1′), and R_(2′) are each independently—C_(x′)F_(y′)H_(z′), 1≤x′≤6, y′>0, z′>0, and 0≤y′≤2x′, 0≤z′≤2x′, and R₇,R₈, R₉, R₁₀, R₁₁, and R₁₂ are each independently one of F or H.

In some embodiments, R_(1′) and R_(2′) are each independently selectedfrom the group consisting of —C₂F₄H, —CF₃, —C₃F₆H, —C₂F₃H₂, and —C₃F₄H₃.

In some embodiments, R_(1′) and R_(2′) are each independently selectedfrom the group consisting of —CF₂—CF₂H, —CF₃, —CF₂—CFH—CF₃, —CH₂—CF₃,and —CH₂—CF₂—CHF₂.

In some embodiments, the fluoroether is selected from the followingstructures:

In some embodiments, R₅ and R₆ are each independently selected from thegroup consisting of —C₂F₃H, —CFH, and —CH₂.

In some embodiments, R₅ and R₆ are each independently selected from thegroup consisting of —CH—CF₃, —CHF, and —CH₂.

In some embodiments, the fluorinated carbonate is selected from thegroup consisting of:

In some embodiments, R₅ and R₆ are each independently selected from thegroup consisting of —CH₃, —C₂F₃H₂, —CFH₂, and —C₂FH₄.

In some embodiments, R₅ and R₆ are each independently selected from thegroup consisting of —CH₃, —CH₂—CF₃, —CH₂—F, and —CH₂—CH₂—F.

In some embodiments, the fluorinated carbonate is selected from thegroup consisting of:

In some embodiments, the fluorinated solvent is fluorobenzene (i.e.,monofluorobenzene).

In the secondary battery of the present disclosure, the electrolyticsolution further may contain an additive prone to lose electrons. Theadditive prone to lose electrons can be oxidized into a film in advance,the decomposition of stable lithium salt is further reduced, and thetotal consumption of the electrolytic solution is further reduced, sothat the electrolytic solution in the battery core is sufficient in themiddle stage of cycle, the transmission dynamics of the lithium ion isrelatively good, the interface impedance is relatively low, and finallythe power and performances of the battery core are relatively good inthe middle stage of cycle.

In some embodiments, the additive prone to lose electrons is one or moreselected from the group consisting of phosphite, borate, and phosphate.

In some embodiments, a content of the additive prone to lose electronsin the electrolytic solution is m₃%, and a ratio m₃/α of m₃ to α isoptionally 0.1˜0.9, for example, 0.1˜0.2, 0.2˜0.3, 0.3˜0.4, 0.4˜0.5,0.5˜0.6, 0.6˜0.7, 0.7˜0.8 or 0.8˜0.9.

In some embodiments, the phosphite is

in some embodiments, the phosphate is

and in some embodiments, the borate is

where R₁₃, R₁₄, R₁₅, R₁₆, R₁₇, R₁₈, R₁₉, R₂₀, and R₂₁ are eachindependently selected from the group consisting of: alkyl, fluoroalkyl,silyl, alkenyl, and phenyl.

In some embodiments, R₁₃, R₁₄, and R₁₅ are each independently selectedfrom the group consisting of C₁₋₆ alkyl (e.g., methyl, ethyl) and C₁₋₆fluoroalkyl (e.g., fluoromethyl, fluoroethyl, e.g., —CH₂—CF₃).

In some embodiments, the phosphite is selected from

In some embodiments, R₁₆, R₁₇, and R₁₈ are each independently selectedfrom C₁₋₆ fluoroalkyl (e.g., fluoromethyl, fluoroethyl, e.g., —CH₂—CF₃)and C₁₋₆ alkenyl (e.g., allyl).

In some embodiments, the phosphate is selected from:

In some embodiments, R₁₉, R₂₀, and R₂₁ are each independently selectedfrom the group consisting of C₁₋₆ alkyl (e.g., methyl, ethyl) and C₁₋₆fluoroalkyl (e.g., fluoromethyl, fluoroethyl, e.g., —CH₂—CF₃).

In some embodiments, the borate is selected from

In some embodiments, in the electrolytic solution of the secondarybattery of the present disclosure, the heat stable salt and the additivethat inhibits decomposition of lithium salt are LiFSI and LiSO₃F,respectively. In some preferred embodiments, w, m₁, and α satisfy:1<m₁w/α<14. In some more preferred embodiments, α is 2˜9.5.

In some embodiments, in the secondary battery of the present disclosure,the electrolytic solution contains the heat stable salt LiFSI and theadditive LiSO₃F that inhibits decomposition of lithium salt, and furthercontains a fluorinated solvent selected from the group consisting of:trifluoroethyl methyl carbonate, fluorobenzene, difluoroethylenecarbonate, the fluoroether of formula 1 described above, and a mixedsolvent of trifluoroethyl methyl carbonate/difluoroethylenecarbonate/fluorobenzene (for example, a mixed solvent at a mass ratio of3/1/1). In some preferred embodiments, the content of the fluorinatedsolvent is m₂%, and a ratio m₂/α of m₂ to α is 1˜8.

In some embodiments, in the secondary battery of the present disclosure,the electrolytic solution contains the heat stable salt LiFSI and theadditive LiSO₃F that inhibits decomposition of lithium salt, and furthercontains an additive prone to lose electrons, wherein the additive proneto lose electrons is selected from the group consisting of the additive1, the additive 2, the additive 3, the additive 4, and the additive 5described above. In some preferred embodiments, the content of theadditive prone to lose electrons in the electrolytic solution is m₃%,and a ratio m₃/α of m₃ to α is 0.1˜0.9.

In the secondary battery of the present disclosure, the electrolyticsolution further may contain an organic solvent. The type of the organicsolvent is not particularly limited, and may be selected according toactual requirements. In some embodiments, the organic solvent mayinclude one or more selected from the group consisting of chaincarbonate, cyclic carbonate, and carboxylic ester. In the above, thetypes of the chain carbonate, the cyclic carbonate, and the carboxylicester are not specifically limited, and may be selected according toactual requirements. Optionally, the organic solvent further may includeone or more selected from the group consisting of diethyl carbonate,dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propylcarbonate, ethyl propyl carbonate, ethylene carbonate (EC), propylenecarbonate, butylene carbonate, γ-butyrolactone, methyl formate, ethylacetate, propyl acetate, methyl propionate, ethyl propionate, methylpropionate, and tetrahydrofuran.

In the secondary battery in accordance with the present disclosure, theelectrolytic solution further may contain an additive for improving gasgeneration, storage or power performances of the battery. In someembodiments, the additive may be one or more selected from the groupconsisting of: a cyclic carbonate compound containing an unsaturatedbond, a halogen-substituted cyclic carbonate compound, a sulfate estercompound, a sulfite compound, a sultone compound, a disulfonic acidcompound, a nitrile compound, an aromatic compound, an isocyanatecompound, a phosphazene compound, a cyclic anhydride compound, aphosphite compound, and a carboxylate compound; in the above, the cycliccarbonate compound containing an unsaturated bond and thehalogen-substituted cyclic carbonate compound are different from thecyclic carbonate described in the preceding.

Besides, the secondary battery, the battery module, the battery pack,and the power consumption device of the present disclosure are describedbelow with appropriate reference to the accompanying drawings.

In an embodiment of the present disclosure, a secondary battery isprovided.

Generally, the secondary battery includes a positive electrode plate, anegative electrode plate, an electrolyte, and a separator. In a chargingand discharging process of the battery, active ions are embedded andseparated back and forth between the positive electrode plate and thenegative electrode plate. The electrolyte plays a role of conductingions between the positive electrode plate and the negative electrodeplate. The separator is provided between the positive electrode plateand the negative electrode plate, and mainly plays a role of preventingshort circuit of positive and negative electrodes, and meanwhile canmake the ions pass through.

[Positive Electrode Plate]

In the secondary battery of the present disclosure, the positiveelectrode plate may include a positive electrode current collector and apositive electrode material layer provided on the positive electrodecurrent collector and including a positive electrode active material,and the positive electrode material layer may be provided on a surfaceof the positive electrode current collector, and also may be provided ontwo surfaces of the positive electrode current collector.

In some embodiments, the positive electrode current collector may be ametallic foil or a composite current collector. For example, an aluminumfoil can be used as the metallic foil. The composite current collectormay include a polymer material substrate layer and a metal layer formedon at least one surface of the polymer material substrate layer. Thecomposite current collector can be formed by forming a metal material(aluminum, aluminum alloy, nickel, nickel alloy, titanium, titaniumalloy, silver, and silver alloy, etc.) on a polymer material substrate(e.g., a substrate of polypropylene (PP), polyethylene terephthalate(PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene(PE), etc.).

In some embodiments, the positive active material may use a positiveactive material for the battery well known in the art. As an example,the positive electrode active material may include at least one of thefollowing materials: olivine-structured lithium-containing phosphates,lithium transition metal oxides and their respective modified compounds.However, the present disclosure is not limited to these materials, andother conventional materials that can be used as a positive electrodeactive material of a battery also may be used. These positive electrodeactive materials may be used alone or a combination of two or more maybe used. In the above, examples of the lithium transition metal oxidemay include, but are not limited to, at least one of lithium cobaltoxide (e.g., LiCoO₂), lithium nickel oxide (e.g., LiNiO₂), lithiummanganese oxide (e.g., LiMnO₂, LiMn₂O₄), lithium nickel cobalt oxide,lithium manganese cobalt oxide, lithium nickel manganese oxide, lithiumnickel cobalt manganese oxide (e.g., LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ (alsoreferred to as NCM₃₃₃ for short), LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ (alsoreferred to as NCM₅₂₃ for short), LiNi_(0.5)Co_(0.25)Mn_(0.25)O₂ (alsoreferred to as NCM₂₁₁ for short), LiNi_(0.6)Co_(0.2)Mn_(0.2)C₂ (alsoreferred to as NCM₆₂₂ for short), LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂ (alsoreferred to as NCM₈₁₁ for short)), lithium nickel cobalt aluminum oxide(e.g., liNi_(0.85)Co_(0.15)Al_(0.05)O₂), and modified compounds thereof.Examples of the olivine-structured lithium-containing phosphate mayinclude, but are not limited to, at least one of lithium iron phosphate(e.g., LiFePO₄ (also referred to as LFP for short)), a compositematerial of lithium iron phosphate and carbon, lithium manganesephosphate (e.g., LiMnPO₄), a composite material of lithium manganesephosphate and carbon, lithium manganese iron phosphate, and a compositematerial of lithium manganese iron phosphate and carbon.

In some embodiments, the positive electrode material layer furtheroptionally includes a binder. The types and contents of the conductiveagent and the binder are not specifically limited, and may be selectedaccording to actual requirements. As an example, the binder may includeat least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene(PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer,vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer,tetrafluoroethylene-hexafluoropropylene copolymer, andfluorine-containing acrylate resin.

In some embodiments, the positive electrode material layer furtheroptionally includes a conductive agent. As an example, the conductiveagent may include at least one of superconducting carbon, acetyleneblack, carbon black, ketjen black, carbon dots, carbon nanotubes,graphene, and carbon nanofibers.

In some embodiments, the positive electrode plate may be prepared in afollowing manner: dispersing the foregoing components for preparing thepositive electrode plate, for example, the positive electrode activematerial, the conductive agent, the binder, and any other components ina solvent (for example, N-methylpyrrolidone), to form a positiveelectrode slurry; and coating the positive electrode slurry on thepositive electrode current collector, followed by procedures such asdrying and cold pressing, to obtain the positive electrode plate.

In some embodiments, the positive electrode material layer contains thepositive electrode active material, large single crystal nickel cobaltlithium manganate (NCM₅₂₃), the conductive agent acetylene black, andthe binder polyvinylidene fluoride (PVDF).

[Negative Electrode Plate]

In the secondary battery of the present disclosure, the negativeelectrode plate may include a negative electrode current collector and anegative electrode material layer provided on the negative electrodecurrent collector and including a negative electrode active material,and the negative electrode material layer may be provided on a surfaceof the negative electrode current collector, and also may be provided ontwo surfaces of the negative electrode current collector.

In some embodiments, the negative electrode current collector can be ametallic foil or a composite current collector. For example, a copperfoil can be used as the metallic foil. The composite current collectormay include a polymer material substrate layer and a metal layer formedon at least one surface of the polymer material substrate. The compositecurrent collector can be formed by forming a metal material (copper,copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver,and silver alloy, etc.) on a polymer material substrate (e.g., asubstrate of polypropylene (PP), polyethylene terephthalate (PET),polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE),etc.).

In some embodiments, the negative active material may use a negativeactive material for the battery well known in the art. As an example,the negative electrode active material may include at least one of thefollowing materials: graphite (for example, artificial graphite andnatural graphite), soft carbon, hard carbon, mesocarbon microbead,carbon fiber, carbon nanotube, silicon-based material, tin-basedmaterial, and lithium titanate, etc. The silicon-based material may beat least one selected from the group consisting of elemental silicon, asilicon-oxygen compound, a silicon-carbon composite, a silicon-nitrogencomposite, and a silicon alloy. The tin-based material may be at leastone selected from the group consisting of elemental tin, a tin oxidecompound, and a tin alloy. However, the present disclosure is notlimited to these materials, and other conventional materials that can beused as a negative electrode active material of a battery also may beused. These negative electrode active materials may be used alone or acombination of two or more may be used.

In some embodiments, a negative electrode material layer furtherincludes a binder. The binder may be at least one selected from thegroup consisting of styrene-butadiene rubber (SBR), polyacrylic acid(PAA), polyacrylic acid sodium (PAAS), polyacrylamide (PAM), polyvinylalcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), andcarboxymethyl chitosan (CMCS).

In some embodiments, the negative electrode material layer furtheroptionally includes a conductive agent. The conductive agent may be atleast one selected from the group consisting of superconducting carbon,acetylene black, carbon black, ketjen black, carbon dots, carbonnanotubes, graphene, and carbon nanofibers.

In some embodiments, the negative electrode material layer contains thenegative active material artificial graphite, the conductive agentacetylene black, and the binder styrene-butadiene rubber (SBR).

In some embodiments, the negative electrode material layer furtheroptionally includes other auxiliary agents, for example, a thickeningagent (such as, carboxymethylcellulose sodium (CMC-Na)), etc.

In some embodiments, the negative electrode plate may be prepared in afollowing manner: dispersing the foregoing components for preparing thenegative electrode plate, for example, the negative electrode activematerial, the conductive agent, the binder, and any other components ina solvent (for example, deionized water), to form a negative electrodeslurry; and coating the negative electrode slurry on the negativeelectrode current collector, followed by procedures such as drying andcold pressing, to obtain the negative electrode plate.

[Separator]

In the secondary battery of the present disclosure, the separator isprovided between the positive electrode plate and the negative electrodeplate, and serves a function of separation. In the above, the type ofthe separator is not specifically limited, and any well-knownporous-structured separator having good chemical stability andmechanical stability can be selected. In some embodiments, the materialof the separator may be at least one selected from the group consistingof glass fiber, non-woven fabric, polyethylene, polypropylene, andpolyvinylidene fluoride. The separator may be a single-layer thin film,and also may be a multi-layer composite thin film, which is notparticularly limited. When the separator is a multi-layer composite thinfilm, materials of various layers may be the same or different, and arenot particularly limited.

The secondary battery of the present disclosure may be a lithium-ionbattery.

The secondary battery of the present disclosure may be prepared by aconventional method. In some embodiments, the positive electrode plate,the negative electrode plate, and the separator may be fabricated intoan electrode assembly through a winding process or a lamination process.An exemplary preparation method includes:

-   -   step 1: stacking the positive electrode plate, the separator,        and the negative electrode plate in sequence, so that the        separator is located between the positive and negative electrode        plates, and then winding them to obtain an electrode assembly;        and    -   step 2: disposing the electrode assembly in a secondary battery        housing, after drying, injecting an electrolytic solution, and        then carrying out formation and standing processes to obtain a        secondary battery.

In some embodiments, the secondary battery of the present disclosure maycontain an outer package. The outer package can be used to encapsulatethe above electrode assembly and electrolyte.

In some embodiments, the outer package of the secondary battery may be ahard shell, for example, a hard plastic shell, an aluminum shell, asteel shell, etc. The outer package of the secondary battery also may bea soft package, for example, a pouch type soft package. The material ofthe soft package may be plastic, and examples of the plastic may includepolypropylene, polybutylene terephthalate, and polybutylene succinate,etc.

There is no particular limitation on the shape of the secondary batteryin the present disclosure, and it may be cylindrical, square or in anyother arbitrary shapes. For example, FIG. 5 shows a secondary battery 5in a square structure as an example.

In some embodiments, referring to FIG. 6 , the outer package may includea housing 51 and a cover plate 53. In the above, the housing 51 mayinclude a bottom plate and a side plate connected to the bottom plate,and the bottom plate and the side plate are enclosed to form anaccommodating cavity. The housing 51 has an opening in communicationwith the accommodating cavity, and the cover plate 53 can be provided tocover the opening so as to close the accommodating cavity. The positiveelectrode plate, the negative electrode plate, and the separator canform an electrode assembly 52 through a winding process or a laminationprocess. The electrode assembly 52 is encapsulated in the accommodatingcavity. The electrolytic solution is soaked in the electrode assembly52. The number of electrode assemblies 52 contained in the secondarybattery 5 can be one or more, and those skilled in the art could make aselection according to actual requirements.

In some embodiments, the secondary batteries can be assembled into abattery module, the number of secondary batteries contained in thebattery module may be one or more, and those skilled in the art couldselect the specific number according to the application and capacity ofthe battery module.

FIG. 3 shows a battery module 4 as an example. Referring to FIG. 3 , inthe battery module 4, a plurality of secondary batteries 5 may besequentially arranged in a longitudinal direction of the battery module4. Without doubt, the secondary batteries 5 also may be arranged in anyother manners. Further, the plurality of secondary batteries 5 may befixed by fasteners.

Optionally, the battery module 4 further may include an enclosure havingan accommodating space, and the plurality of secondary batteries 5 areaccommodated in the accommodating space.

In some embodiments, the above battery module further may be assembledinto a battery pack, the number of battery modules contained by thebattery pack may be one or more, and the specific number can be selectedby those skilled in the art according to the application and capacity ofthe battery pack.

FIG. 4 and FIG. 5 show a battery pack 1 as an example. Referring to FIG.4 and FIG. 5 , a battery box and a plurality of battery modules 4provided in the battery box may be included in the battery pack 1. Thebattery box includes an upper box body 2 and a lower box body 3, and theupper box body 2 can be provided to cover the lower box body 3, and forman enclosed space for accommodating the battery modules 4. The pluralityof battery modules 4 may be arranged in the battery box in an arbitrarymanner.

In addition, the present disclosure further provides a power consumptiondevice, wherein the power consumption device includes the secondarybattery, the battery module or the battery pack provided in the presentdisclosure. The secondary battery, the battery module, or the batterypack can be used as a power supply of the power consumption device, andalso may be used as an energy storage unit of the power consumptiondevice. The power consumption device may be selected from a mobiledevice (for example, a mobile phone, a notebook computer, etc.), anelectric vehicle (for example, a battery electric vehicle, a hybridelectric vehicle, a plug-in hybrid electric vehicle, an electricbicycle, an electric scooter, an electric golf cart, an electric truck,etc.), an electric train, a ship and a satellite, an energy storagesystem, etc., but is not limited thereto. For the power consumptiondevice, the secondary battery, the battery module or the battery packmay be selected in accordance with use requirements thereof.

FIG. 6 shows the power consumption device as an example. This powerconsumption device is a battery electric vehicle, a hybrid electricvehicle, a plug-in hybrid electric vehicle, etc. In order to meet therequirements of the power consumption device for high power and highenergy density of the secondary battery, the battery pack or the batterymodule may be used.

The device as another example may be a mobile phone, a tablet computer,a notebook computer, etc. The device is generally required to be lightand thin, and may use the secondary battery as a power supply.

Example

Hereinafter, examples of the present disclosure are described. Theexamples described below are exemplary, and merely used to explain thepresent disclosure, but cannot be construed as limitation to the presentdisclosure. Where specific techniques or conditions are not specified inthe examples, they are carried out according to techniques or conditionsdescribed in documents in the art or according to productspecifications. If manufacturers of reagents or apparatuses used are notspecified, all of them are conventional products commercially available.

The lithium-ion batteries of the examples and comparative examples areall prepared according to the following method

(1) Preparation of Positive Electrode Plate

A positive electrode active material NCM₅₂₃, a conductive agentacetylene black, and a binder polyvinylidene fluoride (PVDF) weredissolved in a solvent N-methylpyrrolidone (NMP) at a weight ratio of96.5:1.5:2, and fully stirred and well mixed to obtain a positiveelectrode slurry; then, the positive electrode slurry was uniformlycoated on a positive electrode current collector with a coating weightof 18.18 mg/cm², followed by drying, cold pressing, and splitting, toobtain a positive electrode plate.

(2) Preparation of Negative Electrode Plate

An active substance artificial graphite, the conductive agent acetyleneblack, a binder styrene-butadiene rubber (SBR), and a thickening agentcarboxymethylcellulose sodium (CMC-Na) were dissolved in a solventdeionized water at a weight ratio of 95:2:2:1 and well mixed with thesolvent deionized water to prepare a negative electrode slurry; then,the negative electrode slurry was uniformly coated on a negativeelectrode current collector copper foil, with a coating weight of 10.58mg/cm², followed by drying to obtain a negative electrode film sheet,and then the negative electrode film sheet was subjected to coldpressing and splitting to obtain a negative electrode plate.

(3) Preparation of Electrolytic Solution

In an argon-atmosphere glovebox (H₂O<0.1 ppm, O₂<0.1 ppm), organicsolvents EC/EMC were well mixed at a mass ratio of 3/7, and salts andadditives shown in Tables 1-4 were added and well stirred, to obtain acorresponding electrolytic solution.

(4) Preparation of Separator: A Polypropylene Film was Used as aSeparator.

(5) Method of Measuring Cross-Sectional Area S of Tab

A battery core was disassembled, then a thickness h (μm) of a positiveelectrode tab was measured with a micrometer, an average width L (mm) ofthe tab was measured with a conventional ruler, and the total number ofpositive electrode tabs in a single battery core was n, then an averagecross-sectional area S of the positive electrode tabs of thecorresponding single battery core was: n×L×h/1000 (mm²)

(6) Preparation of Lithium-Ion Battery

The positive electrode plate, the separator, and the negative electrodeplate was stacked in sequence, so that the separator was located betweenthe positive and negative electrode plates and served a functionseparation, and then they were wound to obtain an electrode assembly;the electrode assembly was placed in a battery housing, and dried, thenan electrolytic solution was injected, followed by processes such asformation and standing to obtain a lithium-ion battery. The mass of theelectrolytic solution was n₄ (g), where n₄=2.8 g/A·h×C, where 2.8 g/A·hdenotes an injection coefficient, and C denotes capacity of the batterycore (unit: A·h).

A process of testing the lithium-ion battery is as follows:

(1) Testing Capacity of Battery Core

At 25° C., the lithium-ion battery was charged to 4.35 V at a constantcurrent of 1 C, then charged to a current of less than 0.05 C at aconstant voltage of 4.35 V, and then discharged again to 2.8 V at 0.33C, to obtain a discharge capacity C (unit: A·h).

2. Testing Cycle Performance of Lithium-Ion Battery at 45° C.

At 45° C., the lithium-ion battery was charged to 4.35 V at a constantcurrent of 1.5 C, then charged to a current of less than 0.05 C at aconstant voltage of 4.35 V, and then the lithium-ion battery wasdischarged to 2.8 V at a constant current of 1.5 C. This is a charge anddischarge process. Charge and discharge was carried out repeatedly inthis way, for 500 cycles.

3. Internal Resistance of Battery Core

The amount of power of the above battery core having undergone 500cycles was adjusted to 50% SOC, then an internal resistance of thebattery was tested with an AC internal resistance tester, wherein theperturbation was 5 mv, and the frequency was 1000 Hertz.

4. Testing Electrolytic Solution

The weight of the above battery core having undergone 500 cycles wasweighed on a balance and recorded as n₁(g), the above battery corehaving undergone 500 cycles was discharged to 2.8 V at a constantcurrent of 0.1 C, then centrifuged (5000 rpm×30 min). The electrolyticsolution was subjected to ion chromatography analysis to obtain acorresponding lithium salt content w₂. A process of ion chromatographyanalysis was weighing the sample, diluting and dosing the sample withdeionized water, and detecting an anion content of the treated samplewith Dionex ICS-900 instrument.

The electrode plates and the separator of the battery core were soakedin DMC for 3 times to fully remove the electrolytic solution remainingin the electrode plates and the separator, then, the outer package ofthe battery core, the electrode plates, and the separator were all driedin vacuum at 60° C. for 24 h, then weighed, and recorded as n₂(g), thenthe mass of the remaining electrolytic solution of the correspondingbattery core was n₃(g)=n₁−n₂, and the mass fraction of the correspondingremaining electrolytic solution was n₃/n₄.

The mass of the lithium salt in the remaining electrolytic solution wasw₂×n₃, and the mass of the lithium salt in the electrolytic solutioninitially injected into the battery core was w₂×n₄. The mass fraction ofthe lithium salt in the remaining electrolytic solution was: the mass ofthe lithium salt in the remaining electrolytic solution/the mass of thelithium salt in the electrolytic solution initially injected into thebattery core×100%, i.e., (w₂×n₃)/(w₂×n₄).

See Tables 1-4 for test results.

TABLE 1 percentage of remaining lithium internal tab remaining saltcontent in resistance cross- battery centrifuged centrifuged of batterysectional core LiFSI LiSO₃F electrolytic electrolytic core after areacapacity concentration/ content/ solution solution 500 cls No. S/mm²C/A.h α % w % mi m₁w/α after 500 cls after 500 cls mΩ Comparative 24.96280 5.60 0 0 0.00 64.1% 69.2% 0.823 Example 1 Comparative 24.96 280 5.6018 0 0.00 65.8% 72.3% 0.765 Example 2 Comparative 24.96 280 5.60 0 2 065.3% 69.8% 0.782 Example 3 Comparative 24.96 280 5.60 15 0.15 0.4075.1% 81.6% 0.653 Example 4 Example 1 24.96 280 5.60 10 0.3 0.54 84.2%85.2% 0.562 Example 2 24.96 280 5.60 25 4.4 19.63 84.5% 85.5% 0.533Example 3 24.96 280 5.60 22 3.5 13.7 86.4% 87.2% 0.495 Example 4 24.96280 5.60 18 2 6.4 86.0% 87.9% 0.499 Comparative 24.96 280 5.60 30 5 26.875.3% 82.3% 0.622 Example 5 Note: the lithium salt in ComparativeExample 3 is LiFP6, accounting for 18% of the mass fraction of theelectrolytic solution.

From Table 1, it can be seen that the heat stable salt LiFSI or theadditive LiSO₃F that inhibits lithium salt decomposition is not added tothe electrolytic solution of Comparative Example 1, LiSO₃F is not addedto Comparative Example 2, LiFSI is not added to Comparative Example 3,after 500 cycles, more electrolytic solutions are decomposed, thecontent of remaining lithium salt in the electrolytic solution is lower,and the internal resistance of the battery core is higher. The m₁w/α ofComparative Example 4 is less than 0.5, and the m₁w/α of ComparativeExample 5 is greater than 20, and compared with Examples 1-4, moreelectrolytic solutions are decomposed after 500 cycles, the content ofthe remaining lithium salt in the electrolytic solution is relativelylow, and the internal resistance of the battery core is relatively highin Comparative Examples 4 and 5.

TABLE 2 percentage remaining of lithium salt internal remaining contentin resistance tab cross- battery centrifuged centrifuged of batterysectional core LiFSI LiSO₃F electrolytic electrolytic core after energyarea capacity concentration/ content/ solution solution 500 cls densityNo. S/mm² C/A.h α % w % m₁ m₁w/α after 500cls after 500 cls mΩ Wh/LComparative 234.57 280 1.83 12 0.4 2.626 84.5% 85.7% 0.530 498.3 Example6 Comparative 17.28 410 9.86 12 0.4 0.487 76.1% 82.5% 0.581 581.4Example 7 Example 5 9.6 280 9.04 12 0.4 0.531 83.7% 85.1% 0.571 578.7Example 6 156.38 280 2.24 12 0.4 2.144 84.1% 86.0% 0.559 541.2

From Table 2, it can be seen that the m₁w/α of Comparative Example 7 isless than 0.5, and the temperature rise coefficient of ComparativeExample 6 is smaller than 2, and compared with Examples 5 and 6, moreelectrolytic solutions are decomposed after 500 cycles, the content ofthe remaining lithium salt in the electrolytic solution is relativelylow, and the internal resistance of the battery core is relatively highin Comparative Examples 6 and 7.

TABLE 3 remaining lithium percentage salt internal of content resistanceaddition remaining in of tab amount/ centrifuged centrifuged batterycross- battery LiFSI % of electrolytic electrolytic core sectional coreconcen- LiSO₃F type of fluorinated solution solution after area capacitytration/ content/ fluorinated solvent after after 500 cls No. S/mm²C/A.h α % w % m₁ m₁w/α solvent m₂ m₂/α 500 cls 500 cls mΩ Compar- 24.96280 5.60 18 2 6.4 / / / 86.0% 87.9% 0.499 ative Example 8 Compar- 24.96280 5.60 18 2 6.423 trifluoroethyl 3 0.54 86.6% 89.5% 0.485 ative methylcarbonate Example 9 Example 24.96 280 5.60 18 2 6.423 trifluoroethyl 61.07 87.5% 90.1% 0.474 7 methyl carbonate Example 24.96 280 5.60 18 26.423 trifluoroethyl 45 8.03 87.6% 90.7% 0.471 8 methyl carbonateCompar- 24.96 280 5.60 18 2 6.423 trifluoroethyl 60 10.71 87.9% 91.4%0.483 ative methyl carbonate Example 10 Example 24.96 280 5.60 18 26.423 fluorobenzene 6 1.07 87.3% 90.0% 0.475 9 Example 24.96 280 5.60 182 6.423 difluoroethylene 6 1.07 87.4% 90.0% 0.474 10 carbonate Example24.96 280 5.60 18 2 6.423 fluoroether of 6 1.07 87.3% 90.0% 0.476 11formula 1 Example 24.96 280 5.60 18 2 6.423 trifluoroethyl 6 1.07 87.6%90.2% 0.470 12 methyl carbonate/ difluoroethylene carbonate/fluorobenzene = 3/1/1 (mass ratio)

From Table 3, it can be seen that the m₂/α of Comparative Example 9 issmaller than 1, the m₂/α of Comparative Example 10 is greater than 10,and the m₂/α of Examples 7 and 8 is 1%˜8% (after rounding). Comparedwith Examples 7 and 8, the internal resistance of the battery core isslightly high after 500 cycles in Comparative Examples 9 and 10.

TABLE 4 remaining lithium percentage salt of content content remainingin internal of tab centrifuged centrifuged resistance type of additivecross- battery LiFSI electrolytic electrolytic of battery additive pronesectional core concen- LiSO₃F solution solution core after prone to losearea capacity tration/ content/ after after 500 cls to lose electrons/No. S/mm² C/A.h α % w % m₁ m₁w/α 500 cls 500 cls mΩ electrons % m₃ m₃/αCompar- 24.96 280 5.60 18 2 6.423 86.0% 87.9% 0.499 / 0 0 ative Example11 Compar- 24.96 280 5.60 18 2 6.423 86.7% 90.3% 0.470 additive 0.20.036 ative 1 Example 12 Example 24.96 280 5.60 18 2 6.423 87.4% 90.2%0.466 additive 0.57 0.102 13 1 Example 24.96 280 5.60 18 2 6.423 86.6%89.6% 0.461 additive 5 0.892 14 1 Example 24.96 280 5.60 18 2 6.42387.7% 91.2% 0.454 additive 4.5 0.803 15 1 Example 24.96 280 5.60 18 26.423 87.4% 90.3% 0.464 additive 1.2 0.214 16 2 Example 24.96 280 5.6018 2 6.423 87.5% 90.5% 0.463 additive 1.2 0.214 17 3 Example 24.96 2805.60 18 2 6.423 87.4% 90.3% 0.464 additive 1.2 0.214 18 4 Example 24.96280 5.60 18 2 6.423 87.3% 90.0% 0.468 additive 1.2 0.214 19 5

From Table 4, it can be seen that the additive prone to lose electronsis not added to the electrolytic solution of Comparative Example 11, andcompared with Comparative Example 12 and Examples 13-19, moreelectrolytic solutions are decomposed after 500 cycles, the content oflithium salt remaining in the electrolytic solution is relatively low,and the internal resistance of the battery core is higher in ComparativeExample 11. The m₃/a of Comparative Example 12 is less than 0.1%, andthe internal resistance of the battery core after 500 cycles is higherin Comparative Example 12 than in Example 13.

It should be noted that the present disclosure is not limited to theabove embodiments. The above embodiments are merely exemplary, andembodiments having substantially the same configuration as the technicalidea and exerting the same effects within the scope of the technicalsolutions of the present disclosure are all included in the technicalscope of the present disclosure. In addition, in the scope withoutdeparting from the gist of the present disclosure, other modesconstructed by applying various modifications that can be conceived bythose skilled in the art to the embodiment, and combining some of theconstituent elements of the embodiments are also included in the scopeof the present disclosure.

What is claimed is:
 1. A secondary battery, comprising an electrodeassembly and an electrolytic solution, the electrode assembly comprisinga positive electrode plate, a negative electrode plate, and a separator,the positive electrode plate comprising a positive electrode tab, andthe negative electrode plate comprising a negative electrode tab,wherein the positive electrode tab has a following temperature risecoefficient α A.h/mm: $\alpha = \frac{C}{10\sqrt{S1}}$ where S1 is atotal cross-sectional area of the positive electrode tab, in unit ofmm²; C is capacity of the electrode assembly, in unit of Ah, wherein αis from 2 to 9.5; the electrolytic solution contains a heat stable saltand an additive that inhibits decomposition of lithium salt, wherein theheat stable salt has a following molecular formula:(M^(y+))_(x/y)R₁(SO₂N)_(x)SO₂R₂, wherein M^(y+) is one or more selectedfrom the group consisting of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Ba²⁺,Al³⁺, Fe²⁺, Fe³⁺, Ni²⁺, and Ni³⁺, optionally, M^(y+) is one or moreselected from the group consisting of Li⁺, K⁺, Cs⁺, and Ba²⁺, and y isvalence of the M, the R₁ and R₂ are each independently selected from thegroup consisting of fluorine atom, fluoroalkyl having 1˜20 carbon atoms,fluoroalkoxy having 1˜20 carbon atoms, and alkyl having 1˜20 carbonatoms, x is an integer selected from the group consisting of 1, 2, and3, by mass percentage, a content of the heat stable salt in theelectrolytic solution is w %, wherein w % is from 8% to 30%, theadditive that inhibits decomposition of lithium salt is one or more ofRSO₃F, where R is one or more selected from the group consisting of Li⁺,Na⁺, K⁺, Rb⁺, and Cs⁺, by mass percentage, a content of the additivethat inhibits decomposition of lithium salt in the electrolytic solutionis m₁%, wherein m₁% is from 0.1% to 5%, and w, m₁, and α satisfy0.5<m₁w/α<20.
 2. The secondary battery according to claim 1, wherein theheat stable salt has a temperature corresponding to 5% weight loss ratehigher than 200° C.
 3. The secondary battery according to claim 1,wherein in the molecular formula of the heat stable salt, x=1 and y=1,or x=1 and y=2, or x=2 and y=1.
 4. The secondary battery according toclaim 1, wherein in the molecular formula of the heat stable salt, R₁and R₂ are each independently selected from fluorine atom andtrifluoromethyl; and optionally, R₁ and R₂ are both fluorine atom orboth trifluoromethyl.
 5. The secondary battery according to claim 1,wherein the heat stable salt is one or more selected from the groupconsisting of: lithium bisfluorosulfonyl imide, potassiumbisfluorosulfonyl imide, cesium bisfluorosulfonyl imide, bariumbisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide,Li₂F(SO₂N)₂SO₂F, and LiCF₃SO₂NSO₂F.
 6. The secondary battery accordingto claim 1, wherein the additive that inhibits decomposition of lithiumsalt is one or more of LiSO₃F, NaSO₃F, or KSO₃F.
 7. The secondarybattery according to claim 1, wherein the electrolytic solution furthercontains a fluorinated solvent, and the fluorinated solvent is one ormore selected from the group consisting of fluorinated carbonate,fluorobenzene, and fluoroether.
 8. The secondary battery according toclaim 7, wherein a content of the fluorinated solvent in theelectrolytic solution is m₂%, m₂% is from 3% to 60%, and a ratio m₂/α ofm₂ to α is 1˜8.
 9. The secondary battery according to claim 7, whereinthe fluorinated carbonate is

and/or, the fluorobenzene is

and/or, the fluoroether is R_(1′)—O—R_(2′), where R₃, R₄, R₅, R₆,R_(1′), and R_(2′) are each independently —C_(x′)F_(y′)H_(z′), 1≤x′≤6,y′>0, z′>0, and 0≤y′≤2x′, 0≤z′≤2x′, and R₇, R₈, R₉, R₁₀, R₁₁, and R₁₂are each independently one of F or H.
 10. The secondary batteryaccording to claim 9, wherein R_(1′) and R_(2′) are each independentlyselected from a group consisting of —C₂F₄H, —CF₃, —C₃F₆H, —C₂F₃H₂, and—C₃F₄H₃; optionally, R_(1′) and R_(2′) are each independently selectedfrom the group consisting of —CF₂—CF₂H, —CF₃, —CF₂—CFH—CF₃, —CH₂—CF₃,and —CH₂—CF₂—CHF₂; and optionally, the fluoroether is selected fromfollowing structures:


11. The secondary battery according to claim 9, wherein R₅ and R₆ areeach independently selected from a group consisting of —C₂F₃H, —CFH, and—CH₂; optionally, R₅ and R₆ are each independently selected from thegroup consisting of —CH—CF₃, —CHF, and —CH₂; and optionally, thefluorinated carbonate is selected from the group consisting of:


12. The secondary battery according to claim 9, wherein R₅ and R₆ areeach independently selected from a group consisting of —CH₃, —C₂F₃H₂,—CFH₂, and —C₂FH₄; optionally, R₅ and R₆ are each independently selectedfrom the group consisting of —CH₃, —CH₂—CF₃, —CH₂—F, and —CH₂—CH₂—F; andoptionally, the fluorinated carbonate is selected from the groupconsisting of:


13. The secondary battery according to claim 1, wherein the electrolyticsolution further contains an additive prone to lose electrons, and theadditive prone to lose electrons is one or more selected from the groupconsisting of phosphite, borate, and phosphate.
 14. The secondarybattery according to claim 13, wherein a content of the additive proneto lose electrons in the electrolytic solution is m₃%, m₃% is from 0.5%to 1.2%, and a ratio m₃/α of m₃ to α is 0.1˜0.9.
 15. The secondarybattery according to claim 13, wherein the phosphite is

and/or, the phosphate is

and/or, the borate is

where R₁₃, R₁₄, R₁₅, R₁₆, R₁₇, R₁₈, R₁₉, R₂₀, and R₂₁ are eachindependently selected from the group consisting of: alkyl, fluoroalkyl,silyl, alkenyl, and phenyl.
 16. The secondary battery according to claim15, wherein R₁₃, R₁₄, and R₁₅ are each independently selected from thegroup consisting of C₁₋₆ alkyl (e.g., methyl, ethyl) and C₁₋₆fluoroalkyl (e.g., fluoromethyl, fluoroethyl, e.g., —CH₂—CF₃); andoptionally, the phosphite is selected from


17. The secondary battery according to claim 15, wherein R₁₆, R₁₇, andR₁₈ are each independently selected from C₁₋₆ fluoroalkyl (e.g.,fluoromethyl, fluoroethyl, e.g., —CH₂—CF₃) and C₁₋₆ alkenyl (e.g.,allyl); and optionally, the phosphate is selected from:


18. The secondary battery according to claim 15, wherein R₁₉, R₂₀, andR₂₁ are each independently selected from the group consisting of C₁₋₆alkyl (e.g., methyl, ethyl) and C₁₋₆ fluoroalkyl (e.g., fluoromethyl,fluoroethyl, e.g., —CH₂—CF₃); and optionally, the borate is selectedfrom


19. A battery module, comprising the secondary battery according toclaim 1.